This invention relates to thin film magnetic transducer heads and in particular to magnetic heads including a magnetoresistive layer and a soft adjacent layer for biasing.
The use of a magnetoresistive (MR) sensor to sense or read magnetically recorded data is well known in the art. Also well known is the use of both longitudinal and transverse bias to eliminate Barkhausen noise and to maintain the sensor in its most linear operating range.
An objective in the design of disk drives is to use MR sensors having reduced sizes to facilitate the recording of data on reduced track width media, i.e., increased track density media. As an example, U.S. Pat. No. 5,018,037, issued to Krounbi et al., describes an MR read transducer having a central active region and passive end regions. The end regions of this MR sensor have hard magnetic bias layers which generate a longitudinal bias. The central active region contains a soft adjacent layer (SAL) for transverse biasing. The device described in the patent allows the design of smaller transducers to read the data recorded on reduced track widths at increased recording densities.
Another problem facing the magnetic recording industry is that sufficient sense current to saturate the soft adjacent layer is difficult to achieve in read transducers having reduced sizes. In the Krounbi '037 sensor, the moment ratio between the MR layer and the soft adjacent layer (SAL) assists in saturating the SAL when a sense current is applied. However, the current required to saturate the SAL is on the order of 10 milliamps (mA). In certain applications, this sense current magnitude is especially undesirable. Examples of such applications include small disk drives and narrow gap sensors, in which high current densities are required to properly saturate the soft adjacent layer.